Welded truss



June 4- J. E. WEBSTER 1,963,184

WELDED TRUS S Filed June 50, 1932 W|TNE/- ES INVENTOR I ./o/m E/Vebs/ecPatented June 19, 1934 UNITED STATES PATENT OFFICE WELDED TRUSSPennsylvania Application June 30, 1932, Serial No. 620,112

11 Claims.

My invention relates, generally, to building construction and it hasparticular relation to the fabrication of trusses to be used in buildingconstruction.

In the past, it has been customary in the construction of flat roofs andthe like to use I beams for supporting the roof or to use a fabricatedbeam, the upper and lower chords of which are of uniform cross-sectionalarea. With this type of construction, it is necessary to proportion thesupporting member or truss to withstand the maximum stress, which occursin the supporting member at the center when it is symmetrically loaded,and to use the same size of members not only at the location of maximumstress but also to use the same size of members at other points wherethe stress is considerably less. Thus, it is necessary to use a greateramount of material than would be necessary if all of the sectionsforming the support for the desired load were designed to be uniformlystressed.

It is, therefore, an object of my invention to provide a fabricatedtruss which shall be of minimum weight to withstand a given load andwhich may be readily and economically manufactured and installed inposition.

The principal object of my invention is to provide for uniformlydistributing the stresses in the members of a fabricated truss.

Another object of my invention is to provide for uniformly stressing anunder chord member of a truss throughout its entire length.

Still another object of my invention is to provide for a minimum numberof tension members in a truss.

Other objects of my invention will, in part, be obvious and, in part,appear hereinafter.

My invention, accordingly, is disclosed in the embodiment hereof shownin the accompanying drawing, and comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of myinvention, reference may had to the following detailed description takenin connection with the accompanying drawing, in which: I

Figure 1 is a view, in side elevation, of a truss constructed inaccordance with this invention;

Fig. 2 is an enlarged sectional view taken along the line IIII of Fig.1, and.

Fig. 3 is a'fragmentary view of a modification of the truss shown inFig. 1 showing the center panel only.

Referring now to Figs. 1 and 2 of the drawing, the truss there showncomprises an upper chord 10 of webbed beam construction in the form ofan inverted T. As will be readily understood the upper chord 10 isstressed in compression when the truss is loaded. The upper chord 10 maybe of the customary rolled construction which is easily obtainable fromthe manufacturers of structural steel. While the upper chord 10 isillustrated as having a T section, it will be readily apparent that itmay be of any other suitable section such as an I section or the like.However, it is preferable to use the T section in the embodiment of theinvention illustrated in the drawing.

In order to provide the desired rigidity in the truss, lower chords 11,12 and 13 are provided and are secured at spaced intervals to the underside of the chord 10, as illustrated. The lower chords 11, 12 and 13 areof continuous strap construction having a rectangular cross-section.Each of the lower chords is provided with a centrally located straightportion having the ends bent upwardly at uniform angles to meet theunder side of the upper chord 10.

The lower chord 11 is centrally located along the upper chord 10. Eachsucceeding chord, 12 and 13, is disposed in overlapping relation aroundthe centrally located chord 11 so that the distance between eachsuccessive joint of the lower chords 11, 12 and 13 with the upper chord10 is the same.

The load which may be applied to the upper chord 10, as indicated by thearrows, is transmitted to the lower chords 11, 12 and 13 by means ofstruts 14. The struts 14 are preferably of T section since this shapelends itself readily to fabrication. However, a channel section may alsobe used to advantage for the strut 14.

The lower chords 11, 12 and 13 and the struts 14 are preferably securedtogether and to the upper chord 10 by means of arc welded joints. Whilea riveted joint maybe used in practicing the invention, the particularform of construction of the truss does not lend itself readily to thistype of joint and, therefore, its use is not feasible. The arc weldedjoint provides a very cheap and strong connection between the elementsof the truss and fashions it into an integral structure of minimumweight for a given loading.

It will be observed that the lower chords 11,

12 and 13 will be stressed in tension when the truss is loaded asindicated by the arrows. It is desirable to apply the tension stress tothese lower chords 11 12 and 13 uniformly throughout their length. Thedesired uniform stressing of the lower chords 11, 12 and 13 is obtainedby positioning the struts 14 to bisect the angle formed between thestraight central portion and the upwardly turned ends of the lowerchords 11, 12 and 13.

As is particularly shown in the drawing at the left hand end of thetruss, the anglesA- and B are equal. With this form of construction, anystress which occurs in the bent portion of the lower chord 13 istransmitted undiminished to the remaining portion thereof. The struts 14are then subject only to a compressive force and no torsional stress isapplied thereto.

While a single strut 14' is illustrated in the drawing, it will bereadily apparent that two or more angularly disposed struts may beusedin place of a single strut 14, as is desired, when the load appliedto the upper chord 10 is distributed at a greater number of points thanare indicated in the embodiments illustrated.

The joints formed at the junction of the lower chords 11 and 12 and thestruts 14 are so arranged that the lines through the centers of gravityof the bent portions of the lower chords 11 and 12 and of the struts 14intersect along the center of gravity of the upper chord l0.v With thisform of construction, it is possible to transmit the stresses from theupper chord 10 to the lower chords 1i and 12 and the struts 14 with theapplication of a minimum of torsional stress.

In the event that it is desired to provide a truss having an equalnumber of panels in place of the truss having an unequal number, as isillustrated in Fig. 1 of the drawing, the construction illustrated inFig. 3 may be used. I

In the construction illustrated in Fig. 3, a lower chord 15 is bent atits center thereby providing 1 no straight portion as shown in Fig. 1 inthe lower chordll. A single strut 16 may then be used to transmit theload from the upper chord 10- to the lower chord 15 in place of the twostruts 14 used for transmitting the load to the lower chord When thesingle strut 16 is used, it is located at right angles to the upperchord 10 since, in this position, a minimum of torsional stress will beapplied thereto.

It will be readily apparent to those skilled in the art that the totalstress applied to the lower chord 12 is greater thanthat applied to thelower chord 11. Likewise the total stress that isapplied to the lowerchord 13 is greater than that applied to the lower chord 12. It willalso be apparent that none of the stress which is applied to any one ofthe lower chords 11, 12 or 13 is applied to any of the other chords.Therefore, each lower chord member may be proportioned to withstand thestress applied theretowithout reference to the stress in any of theother lower chord members.

As illustrated more clearly in Fig. 2 of the drawing, thecross-sectional area of each succeeding lower chord member after lowerchord 11 may be increased to withstand the stress applied. Thus, eachlower chord member may be proportioned to withstand the stress appliedthereto and, further, no more material than is necessary need 7 be usedfor each lower chord member. At the center of the lower chord members,where the maximum stress is applied, the maximum amount of material isalso present with this type of construction and, as the applied stressdecreases towards the ends of the truss, the

amount of material present decreases somewhat in proportion thereto.

While a truss has been illustrated and described comprising three lowerchords, namely 11, 12 and 13 and a modification thereof as shown in Fig.3, it will be evident that various other modifications of the inventionmay be fabricated without departing from the scope of the invention. Itwill also be apparent that this invention may be practiced in connectionwith the use of a greater or lesser number of panels by increasing thenumber of lower chord members that are used. Therefore, it is intendedthat all matter contained in the above description or illustrated in theaccompanying drawing shall be interpreted as illustrative and not in alimiting sense.

I claim as my invention:

1. A truss for use in building construction comprising an upper chord,and a plurality of underrunning continuous lower chords secured at theends of the under side of the upper chord and spaced therefrom byseparate strut means having column sections, each succeeding lower chordhaving a different cross-sectional area than the preceding lower chordto permit a uniform stress distribution in the lower chords.

2. A truss for use in building construction comprising an upper chord, aplurality of lower chords secured to the upper chord, thecross-sectional, area of each lower chord being substantiallyproportional tothestress applied thereto, and a plurality of pairs of.separate struts having column sections, each pair of struts beingindividual to one of the lower chords and interposed between the upperand lower chords.

3. A truss for use in buildingconstruction comprising an upper chord, aplurality of individual lower chords secured. to the upper chord atspaced intervals along its under surface, the cross-sectional area ofeach lower chord being substan tially proportional to the stress appliedthereto, and a plurality of pairs of separate compression members havingcolumn sections, each pair being individual to one of the lower chordsvand interposed between theupper chord and each of the lower chords;

4. In building construction, a truss comprising an upper chord, aplurality of continuous tension members secured at the ends to the uppercolumn sections interposed between the upper chord and the tensionmembers for spacing them.

apart and transmitting the load applied on the upper chord to thetension members.

5. A truss for use in building construction comprising a continuousupperchord of webbed beam construction serving as a compression member, a.plurality. of continuous lower chords of flat plate construction servingas tension members, the cross-sectional area of each lower chord, beingsubstantially proportional to the stress applied thereto, each of thelower chords being of different length and secured at the ends at spacedintervalsto the underside of the upper chord and overlapping eachsuccessive lower chord, and a plurality of strutsof webbed beamconstruction serving as compression members to space the upper and lowerchords apart.

6. A truss for use in building construction comprising an. upper chordof Webbed beam. construction, a lower chord comprising a plurality ofoverlapping continuous members welded tothe underside of the upperchord, and a plurality of struts having column sections interposedbetween the underside of the upper chord and the members of the lowerchord and welded thereto, the cross-sectional area of each succeedingmember of the lower chord being different than the crosssectional areaof the preceding member to permit a uniform distribution of the stressin each member.

7. A truss for use in building construction comprising an upper chord ofinverted T section, a plurality of lower chords of rectangularcrosssection and of different length secured in overlapping relationwith each succeeding chord at the ends at spaced intervals to theunderside or the upper chord, each of the under chords having a straightcentral portion and a bent portion at each end and each successive.chord being smaller in cross-sectional area than the preceding chord,and a plurality of struts of webbed beam construction interposed betweenthe underside of the upper chord and the lower chords, each of thestruts being positioned to bisect the angle formed between the straightportion and the bent portion of each lower chord to permit a uniformstress distribution throughout the entire length thereof.

8. A truss for use in building construction comprising an upper chord, aplurality of overlapping lower chords of different lengths, each of thelower chords having a centrally located straight portion and a bentportion at each end, the ends of each of the lower chords being weldedto the underside of the upper chord at spaced intervals, and a pluralityof struts interposed between the underside of the upper chord and thelower chords and welded thereto, each of the struts being positioned tobisect the angle formed between the straight portion and the bentportion of each lower chord to permit a uniform stress distributionthroughout the entire length.

9. A truss for use in building construction comprising an upper chord ofwebbed beam construction, a lower chord comprising a continuous strap ofrectangular cross-section secured at the ends in a central position onthe under side of the upper chord and spaced from the underside of saidupper chord midway the ends thereof by separate strut means having acolumn section, and a plurality of additional lower chords symmetricallydisposed in overlapping relation around the centrally located lowerchord and. spaced from the upper chord by additional strut means, eachsucceeding lower chord being of larger cross-sectional area than thepreceding chord to permit a relatively uniform stress distribution ineach of the lower chords.

10. A truss for use in building construction comprising an upper chordof webbed beam construction, a lower chord comprising a continuous strapof rectangular cross-section secured at the ends in a central positionon the under side of the upper chord and spaced therefrom at its centerby a single strut having a column section, and a plurality of additionallower chords symmetrically disposed in overlapping relation around thefirst mentioned lower chord and spaced from the upper chord by a pair ofstruts individual to each additional lower chord, each succeeding lowerchord being of larger cross-sectional area than the preceding chord topermit a relatively uniform stress distribution in each of the lowerchords.

11. A fabricated member for use in building construction or the likecomprising, in combination, an upper chord member of webbed beamconstruction, a plurality of rectangularly shaped overlapping lowerchord members secured to the underside of said upper chord member, thecross sectional areas of said lower chord members being proportioned topermit the application of substantially uniform unit stress thereto, anda plurality of pairs of separate strut members having column sections,said pairs of strut members being individual to each of said lower chordmembers and disposed between the upper and lower chord members fortransmitting stress therebetween.

JOHN E. WEBSTER.

